A GLOF may have diverse causes and subsequent mechanisms, for example accordingly on how water is released. Specific causes are related to specific mechanisms and not all their combinations are realistic scenarios. Moreover, specific subtypes of glacial lakes are susceptible to specific causes and subsequent mechanisms of outburst floods. Numerous studies have investigated the causes of lake outburst floods for specific lake subtypes and regions ; however, systematic investigation of the causes and mechanisms of GLOF, as well as database construction, are required in order to better understand the complex processes and, in turn, provide more effective hazard and risk management (Emmer).
The following direct causes of glacial lake outburst floods were documented:
- Rapid slope movement into the lake
- Heavy rainfall/snowmelt
- Cascading processes (flood from a lake situated upstream)
- Melting of ice incorporated in dam/forming the dam (including volcanic activity-triggered jökulhlaups)
- Blocking of subsurface outflow tunnels (applies only to lakes without surface outflow or lakes with a combination of surface and subsurface outflow)
- Long-term dam degradation (Emmer).